exploring the qcd phase diagram at high baryon densities: the cbm experiment at fair claudia höhne,...

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Exploring the QCD Phase Diagram at High Baryon Densities: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt FAIR QCD phase diagram results from SPS and RHIC CBM physics topics and observables feasibility studies and R&D

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Exploring the QCD Phase Diagram at High Baryon Densities:

The CBM experiment at FAIR

Claudia Höhne, GSI Darmstadt

• FAIR

• QCD phase diagram

• results from SPS and RHIC

• CBM physics topics and observables

feasibility studies and R&D

2 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

FAIR

Facility for Antiproton and Ion Research

• accelerator complex serving several experiments at a time (up to 5) from a broad community

• highest beam intensities! (e.g. 2x1013/s 90 GeV protons and 109 45 AGeV Au ions)

• "working horse": SIS 100 serving a variety of storage rings

• rare isotope beams

• stored and cooled antiprotons

• foundation of FAIR GmbH in summer 2009

• operational ~2016

Observer:EU, United States, Hungary, Georgia, Saudi Arabia

3 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

FAIR accelerator complex

4 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Research programs at FAIR

Beams of antiprotons: hadron physics quark-confinement potential search for gluonic matter and hybrids hypernuclei

PANDA

5 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Research programs at FAIR

NUSTAR

Rare isotope beams; nuclear structure and nuclear astrophysics nuclear structure far off stability nucleosynthesis in stars and supernovae

Super-FRS

6 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Research programs at FAIR

accelerator physics high intensive heavy ion beams (vacuum!) rapidly cycling superconducting magnets high energy electron cooling

short-pulse heavy ion beams: plasma physics matter at high pressure, densities, and temperature fundamentals of nuclear fusion

atomic physics and applied research highly charged atoms low energy antiprotons (anti-hydrogen) radiobiology materials research

7 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

CBM @ FAIR

Outline

• Physics case of CBM• physics topics, observables for CBM• results from SPS and RHIC

• CBM detector, examples for• feasibility studies• R&D

high-energy nucleus-nucleus collisions: compressed baryonic matter baryonic matter at highest densities (neutron stars) phase transitions and critical endpoint in-medium properties of hadrons

8 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

QCD phase diagram at high baryon densities

[F.Karsch, Z. Fodor, S.D.Katz]

• intermediate range of the QCD phase diagram with high net-baryon densities of strong interest because of

• expected structures as 1st order phase transition and critical point (2nd order phase tarnsition)

• chiral phase transition

• deconfinement = chiral phase transition ?

• hadrons and quarks at high ?

• signatures (measurable!) for these structures/ phases?

• how to characterize the medium?

9 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

What do we know from experiment? → Heavy-ion collisions:

• „chemical freeze-out curve“ = (T, B) from statistical model

• top SPS, RHIC (high T, low B): partonic degrees of freedom, crossover (?)

• RHIC: first steps towards a quantitative characterization of the medium (gluon density, viscosity, energy loss...)

• lower SPS (intermediate T-B): intriguing observations around 30 AGeV!

• SIS, AGS: high density baryonic matter

QCD phase diagram & experiments

[Andronic et al. Nucl. Phys. A 772, 167 (2006).

10 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Within the next years we'll get a complete scan of the QCD phase diagram with 2nd generation experiments

• LHC, RHIC: bulk observables and rare probes (charm, dileptons)

• RHIC energy scan: bulk observables√s ~ (5)10 GeV – 200 GeV

• NA61: focus on fluctuations(√sNN = 4.5 – 17.3 GeV), A < 120

• NICA: strangeness, bulk observables (√sNN = 3 – 9 GeV)

• CBM: bulk observables and rare probes (charm, dileptons)beam energy 10 – 45 GeV/nucleon(√sNN = 4.5 – 9.3 GeV)

• HADES: bulk observables, dileptonsbeam energy 2 – 10 GeV/nucleon

Experimental scan of QCD phase diagram

[Andronic et al. Nucl. Phys. A 772, 167 (2006).

HADES

CBM, NA61, NICA

LHCRHIC

FAIR beam intensities: up to 109 ions/s

11 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

SPS results

[Andronic et al. Nucl. Phys. A 772, 167 (2006).]

[NA49, PRC 77, 024903 (2008)]

• energy dedendence of hadron production→ changes in SPS energy regime

• discussions ongoing:• hadron gas → partonic phase • baryon dominated → meson dominated matter

• missing: high precision measurements, systematic investigations, correlations, rare probes→ quantitative characterization of the medium!

12 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

High net-baryon density matter at CBM

• high baryon and energy densities created in central Au+Au collisions

[CB

M p

hysi

cs g

rou

p, C

. F

uchs

, E

. B

ratk

ovsk

aya

priv

. co

m.]

beam energy

max. /0

max [GeV/fm3]

time span

~FWHM

5 AGeV 6 1.5 ~ 8 fm/c

40 AGeV 12 > 10 ~ 3.5 fm/c

16 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

[A. Andronic, P. Braun-Munzinger, K. Redlich, J. Stachel, arXiv:0708.1488]

Statistical hadronization model (SHM)(c-cbar in partonic phase)

O. Linnyk, E.L. Bratkovskaya, W. Cassing, H. Stöcker,Nucl.Phys.A786:183-200,2007

Hadronic model (HSD)

NN → D Λc NNN → DD NNNN → J/ψ NN

Charm production in hadronic and partonic matter

17 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Charm production in hadronic and partonic matter

no charm (J/) data below 158 AGeV beam energy

detailed information including phase space distributions!

18 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

-meson spectral function

• -meson couples to the medium: "melts" close to Tc and at high B

• vacuum lifetime 0 = 1.3 fm/c

• dileptons = penetrating probe

• connection to chiral symmetry restoration?

• particular sensitive to baryon densityp

n

++

p

e+, μ+

e-, μ-

"SPS""FAIR"

[R. Rapp, priv. com. (CBM physics book)]

• illustrate sensitivity to modifications caused by the baryonic component of the medium:

-meson spectral function weighted by 1/M to resemble the dilepton rate, Bose-factor will further amplify the low-mass part

• m < 0.4 GeV/c2 of special interest!

no measurement between 2-40 AGeV beam energy yet!

19 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Dileptons

hep-ph/0604269

• new results from top SPS energy (√sNN = 17.3 GeV):

→ modification of spectral function, importance of baryons!

CERES NA60

• measure in dependence on baryon density (energy)!

20 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Critical point

• critical point = endpoint of 1st order phase transition: 2nd order phase transition

• critical region might be small, focussing effect?

• fluctuations would need time to develop

[Schaefer, Wambach, PRD75, 085015 (2007)] [Asakawa, Bass, Mueller, Nonaka, PRL 101, 122302 (2008)]

21 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Event-by-event fluctuations

[NA49 collaboration, arXiv:0810.5580v2 [nucl-ex]]

• observation might become enormously difficult

• correlation length of sigma field, may become rather small for a finite lifetime of the fireball

• large acceptance needed!

2

2

pt

pt

pt zN

Z

N

ittipt

ttpt

ppZ

ppz

1

[Stephanov, Rajagopal, Shuryak, PRD60, 114028 (1999)]

22 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Event-by-event fluctuations

[NA49 collaboration, arXiv:0810.5580v2 [nucl-ex]]

• observation might become enormously difficult

• correlation length of sigma field, may become rather small for a finite lifetime of the fireball

• large acceptance needed!

2

2

pt

pt

pt zN

Z

N

ittipt

ttpt

ppZ

ppz

1

[Stephanov, Rajagopal, Shuryak, PRD60, 114028 (1999)]

1st try to identify 1st order phase transition line

fluctuations, correlations with large acceptance and particle identification

23 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

CBM: Physics topics and Observables

Onset of chiral symmetry restoration at high B

• in-medium modifications of hadrons (,, e+e-(μ+μ-), D)

Deconfinement phase transition at high B • excitation function and flow of strangeness (K, , , , )• excitation function and flow of charm (J/ψ, ψ', D0, D, c)• charmonium suppression, sequential for J/ψ and ψ' ?

The equation-of-state at high B

• collective flow of hadrons• particle production at threshold energies (open charm)

QCD critical endpoint• excitation function of event-by-event fluctuations (K/π,...)

predictions? clear signatures?→ prepare to measure "everything" including rare probes → systematic studies! (pp, pA, AA, energy)aim: probe & characterize the medium! - importance of rare probes!!

24 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

The CBM experiment• tracking, momentum determination, vertex reconstruction: radiation hard silicon pixel/strip detectors (STS) in a magnetic dipole field

• hadron ID: TOF (& RICH)• photons, 0, : ECAL

• electron ID: RICH & TRD suppression 104

• PSD for event characterization• high speed DAQ and trigger → rare probes!

• muon ID: absorber + detector layer sandwich move out absorbers for hadron runs

RICHTRD

TOF ECAL

magnet

absorber +

detectorsSTS + MVD

25 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

STS tracking – heart of CBM

Challenge: high track density: 600 charged particles in 25o @ 10MHz

Task

• track reconstruction: 0.1 GeV/c < p 10-12 GeV/c p/p ~ 1% (p=1 GeV/c)

• primary and secondary vertex reconstruction (resolution 50 m)

• V0 track pattern recognition

c = 312 m

radiation hard and fast silicon pixel and strip detectors

self triggered FEE

high speed DAQ and trigger

online track reconstruction!

fast & rad. hard detectors!

26 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

• max: up to ~109 tracks/s in the silicon tracker (10 MHz, ~100 tracks/event)

• start scenario for D more like 0.1 MHz → 107 tracks/s

→ fast track reconstruction!

• optimize code, port C++ routines to dedicated hardware

• parallel processing → today: factor 120000 speedup of tracking code achieved!

• long term aim: make use of manycore architectures of new generation graphics cards etc.

Track reconstruction

GeForce 9600

64 core GPU

27 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Double and triple GEM detectors2 Double-sided silicon microstrip detectors

Radiation tolerance studies for readout electronics Full readout and analysis

chain:

Front-end board with self-triggering

n-XYTER chip Readout controllerData Acquisition

System

online

offline

Go4

AnalysisDetector

signals

Successful test of CBM prototype detector systems with free-streaming read-out electronics using proton beams at GSI, September 28-30, 2008

GSI and AGH Krakow VECC Kolkata KIP Heidelberg

28 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

GSI, Darmstadt, GermanyJINR, Dubna, RussiaKIP, Heidelberg, GermanyVECC, Kolkata, IndiaAGH, Krakow, Poland

90Sr -spectra ...

Detector commissioning:

... in several channels of a silicon microstrip detector

... and in a GEM detector

Operation on the beam line:

Participants:

Beam spot seen on a GEM detector (every 2nd channel read out)

Correlation of fired channels in two silicon microstrip detectors

www-cbm.gsi.de

29 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

CBM hardware R&D

RICH mirror

n-XYTER FEB

Silicon microstrip detector

MVD: Cryogenic operation in vacuum RPC R&D

Forward Calorimeter

GEM

dipole magnet

30 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Open charm reconstruction

beam

~mm

Measure , K in

first detector at 5 or 10 cm

c = 312 m

• open charm reconstruction via the reconstruction of their 2ndary decay vertex

• most important features for background rejection• good position resolution of 2ndary decay vertex (~50 m) • good position resolution for back extrapolation of decay particles to primary vertex plane

• thin high resolution detectors needed which are close to the primary vertex!

+

+

K-

D+

31 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Monolithic Acitive Pixel Sensors in commercial CMOS process1010 m2 pixels fabricated, > 99%, x ~ 1.5 – 2.5 m

Micro Vertex Detecor (MVD) DevelopmentArtistic view of the MVD

• mechanical system integration • material for cooling!→ material budget!• vacuum compatibility

die thinned to 50 mglued to support.IPHC, Strasbourg (M. Winter et al.)

32 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

D-meson Simulations• CbmRoot simulation framework, GEANT3 implemented through VMC

• full event reconstruction: track reconstruction, particle-ID (RICH, TRD, TOF), 2ndary vertex finder

• feasibility studies: central Au+Au collisions at 25 AGeV beam energy (UrQMD)

• several channels studied: D0, D±, Ds, c

• here: 2 MAPS layers (10, 20 cm, 150 m Si-equivalent each)

D+ → ++K- (c = 312 m, BR 9%)D0 → K-+ (c = 123 m, BR 3.85%)c → pK-+ (c = 60 m, BR 5%)

33 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

D meson reconstruction

1st MAPS thickness

Position of 1st

D+

efficiency

D+

S/B (2)

D+

in 1012 ev.

150 m 10 cm 4.2% 9 162·103

500 m 10 cm 1.05% 0.93 41·103

300 m 5 cm 2.6% 1.1 103·103

• important layout studies: MAPS position and thickness !

• HSD: <D+> = 4.2 · 10-5/ev

• 1012 central events ~ 8-10 weeks running time

34 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

CBM feasibility studies

• feasibility studies performed for all major channels including event reconstruction and semirealistic detector setup

D0

c

J/ J/

di-electrons di-muons

' '

35 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Challenges of the di-electron measurement

• clean electron identification ( suppression ≥ 104)

• large background from physical sources

-conversions in target and STS, 0 Dalitz decays

→ use excellent tracking and two hit resolution (≤ 100 m) in first pixel detectors in order to reject this background: → optimize detector setup (STS, B-field), use 1‰ interaction target

ee0

ee 0

Track Segment

eemedium

Track Fragment

signal

fake

pair

RICH & TRD

ee

36 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Performance of combined e-ID

• use RICH, TRD (and TOF) detectors for electron identification

• 104 -suppression at ~75% efficiency

• combined purity of identified electrons ~96%

p [GeV/c]p [GeV/c]

37 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Background in electron measurement

K. Antipin, IKF Frankfurt

38 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Detector layout optimization: Muon absorber

40 20 20 20 25

30 20 20 20 35

20 20 20 30 35

10 20 30 30 35

central Au+Au collisions at 25 AGeV10 cm Fe

20 cm Fe

30 cm Fe

40 cm Fe

hit density after 1st absorber

total absorber length 125 cm = 7.5 I

39 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Muon identification

• alternating absorber-detector system allows efficient muon tracking

• central Au+Au collisions, 25 AGeV, absorber layout as (20+20+20+30+35) cm iron, 3 detector stations in between

• certain momentum cutoff depending on absorber length

• main part of remaining background: muons from , K decays

40 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

Dileptons

J/ J/

di-electrons di-muons

' '

very similar performance despite of the different background sources

41 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

CBM@FAIR – high B, moderate T:

• searching for the landmarks of the QCD phase diagram• first order deconfinement phase transition • chiral phase transition• QCD critical endpoint

→ systematic measurements, rare probes

• characterizing properties of baryon dense matter

• in medium properties of hadrons?

in A+A collisions from 10-45 AGeV (√sNN = 4.5 – 9.3 GeV) starting in 2016 at SIS 300

Summary – physics of CBM

42 Claudia Höhne HIM meeting, Muju Resort, Korea, February 2009

CBM collaborationRussia:IHEP ProtvinoINR TroitzkITEP MoscowKRI, St. Petersburg

China:Tsinghua Univ., BeijingCCNU WuhanUSTC Hefei

Croatia:

University of SplitRBI, Zagreb

Portugal: LIP Coimbra

Romania: NIPNE BucharestBucharest University

Poland:Krakow Univ.Warsaw Univ.Silesia Univ. KatowiceNucl. Phys. Inst. Krakow

LIT, JINR DubnaMEPHI MoscowObninsk State Univ.PNPI GatchinaSINP, Moscow State Univ. St. Petersburg Polytec. U.

Ukraine: INR, KievShevchenko Univ. , Kiev

Univ. MannheimUniv. MünsterFZ RossendorfGSI Darmstadt

Czech Republic:CAS, RezTechn. Univ. Prague

France: IPHC StrasbourgGermany: Univ. Heidelberg, Phys. Inst.Univ. HD, Kirchhoff Inst. Univ. Frankfurt

Hungaria:KFKI BudapestEötvös Univ. BudapestIndia:Aligarh Muslim Univ., AligarhIOP BhubaneswarPanjab Univ., ChandigarhGauhati Univ., Guwahati Univ. Rajasthan, JaipurUniv. Jammu, JammuIIT KharagpurSAHA KolkataUniv Calcutta, KolkataVECC Kolkata

Univ. Kashmir, SrinagarBanaras Hindu Univ., Varanasi

Korea:Korea Univ. SeoulPusan National Univ.Norway:Univ. Bergen

Kurchatov Inst. MoscowLHE, JINR DubnaLPP, JINR DubnaCyprus:

Nikosia Univ.

55 institutions, > 400 members

Dubna, Oct 2008